The present invention relates to a capacitive pressure sensor, and particularly to a pressure sensor that is positioned in a tire and communicates information relating to the pressure to a remote interrogator.
Every iteration of vehicle design results in greater complexity for the vehicle in an effort to improve functionality. Vehicles now monitor many parameters that previously had to be addressed through routine maintenance or expensive diagnostics. This monitoring is done by vehicle controllers. By providing this access to information about the vehicle, expectations about possibilities arise and this creates a demand for more information from which to synthesize still further parameters that may improve performance.
Tire pressure monitoring may be important since the pressure in a tire governs its proper operation and safety in use. For example, too little pressure in a tire during its use can cause a tire to be damaged by the weight of a vehicle supported by the tire. Too much pressure can cause a tire to rupture. Tire pressure is currently tested by hand-held devices when the vehicle is stopped, and thus it is difficult to secure tire pressure information while the vehicle is operational.
In related areas, there has been an increase in the desire to track goods as they move through the manufacturing, distribution and retail processes. To that end, many goods are being equipped with radio frequency identification tags (RFID). Tires are an example of such goods that may benefit from the use of a wireless communication device that communicates information regarding the tire, such as a tire's identification, pressure, temperature, and other environmental information. For example, tire pressure must be tested during the manufacturing process to ensure that the tire meets intended design specifications. The tire pressure should also be within certain pressure limits during use to avoid dangerous conditions. Knowledge of the tire pressure during the operation of a vehicle can be used to inform an operator and/or vehicle system that a tire has a dangerous pressure condition.
Thus, there remains a need for a pressure sensor associated with a tire that can wirelessly communicate to a remote location.